Offset printing with alkenylsuccinic acid compound

ABSTRACT

Paper characterized by insoluble basic surface properties is rendered selectively printing-ink receptive by application of alkenylsuccinic acid, its anhydride, or its soluble salt.

United States Patent Keith B. Bozer Midland, Mich.

Mar. 3, 1969 Apr. 13, 1971 The Dow Chemical Company Midland, Mich.

inventor Appl. No. Filed Patented Assignee OFFSET PRINTING WITH ALKENYLSUCCINIC ACID COMPOUND [56] References Cited UNITED STATES PATENTS 2,681,617 6/1954 Worthen et a1. 101/451 3,053,177 9/1962 McHugh et a1.... lOl/460 3,293,186 12/1966 Chu et al. 101/466UX Primary Examiner-David Klein Attorneys-Griswold and Burdick, Thomas J. Page and Al bin R. Lindstrom ABSTRACT: Paper characterized by insoluble basic surface properties is rendered selectively printing-ink receptive by application of alkenylsuccinic acid, its anhydride, or its soluble salt.

OFFSET PRINTING WITH ALKENYLSUCCINIC ACID COMPOUND BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is concerned with offset printing of the kind which, on a venerable history, is oftentimes called lithography. Traditionally, lithography (the name is derived from the Greek lithos meaning stone and grapho meaning write) has involved the preparation to a smooth surface of a stone, usually limestone, which can be a dolomitic limestone, of very fine grain. Upon this stone, by a skilled artist working in mirror image with a lithographers crayon" of a waxy nature, a design to be printed is applied. Thereafter, the surface of the stone is definitively wetted with water, (characteristically in the absence of surface-active agents) and the wetted surface then coated with printer's ink from a roller, which has at times been a roller in a printing press. The ink, characteristically oilor solvent-based in nature, wets, that is to say, adheres by means of hydrogen bonds and by forces such as the forces of van der Waals, to only the waxycoated surface where the lithographers crayon was applied. The phenomenon has admitted of carrying out the practice with such delicacy that great artists from Benjamin West in 1801 to Picasso today have found the lithograph medium an artistic medium of great sensitivity. Other notable contributions to lithography as an artistic medium have been made by Currier and Ives, and mention should be made of a revival of the medium at the hands of James A. MacNeil Whistler. Daumier, Hassam, Signac, Degas, Renoir, Kollwitz, Rouault, Orozco, and Rivera are but a few artists who have found lithography a medium of virtuosity. It is widely used in commercial and industrial printing as well.

In more recent years, the method has been modified. The lithographer's stone has given way to papers and metal plate surfaces. The hydrophobic-hydrophilic balance of inks and of material in the stead of the lithographers crayon have been carefully studied. Because the lithos, or stone has been largely displaced, the process has become known, in more recent years, as offset" printing.

2. The Prior Art As to offset printing or lithography assisted by an alkenylsuccinic acid compound, applicant knows of no prior art whatsoever. The alkenylsuccinic acids, their anhydrides, and their soluble salts such as their alkali metal salts including notably the sodium and disodium salts are well known in the prior art. US. Pat. No. 2,770,077 is concerned with the use of an alkenylsuccinic compound in conditioning soil for agricultural use.

DESCRIPTION OF THE INSTANT INVENTION In the present invention, a printable or printing surface having insoluble basic surface properties is treated, in a design representing printing, with an alkenylsuccinic acid, its anhydride, or its sodium salt. Because these substances are readily soluble in water at rates satisfactory for the present invention, they can be applied in water solution but other forms can also be employed. It is believed but it has not been proved that the succinic acid site reacts in some way with the insoluble basic surface of the paper, leaving the alkenyl relatively hydrophobic chain pendent. The resulting surface, when wetted with water, is sensitive to receive a typical hydrophobic (that is to say, oil-based) printing ink upon only the surfaces where the alkenylsuccinic acid compound has been applied; the hydrophilicity of the other surfaces, when wet, causes them to reject the oil-based printing ink.

The foregoing makes it at once apparent that, if it is desired to do so, a water-based or generally hydrophilic printing ink can be used, with the result that it adheres to the surfaces not treated with the succinic acid compound according to this invention, leading to a reverse image of that obtained with an oil-based ink upon the same surface. This characteristic makes possible unusual versatility in the instant process, as in color printing and the like. Ink of one color may be hydrophilic, for example, and of another may be lipophilic. Thus, a single lithographic plate of this invention may bring two colors to the printed site or printing surface, obviating the possibility of I error in their registry.

In the instant specification and claims, a printable" surface is a surface, such as a paper surface, upon which it is desired to print, more or less permanently, as the finished article. Also, a printing" surface herein is a surface to receive and transfer a printed image to another surface; in the sense of the lithograph stone or lithograph plate, from which a printable surface is to be printed.

In one embodiment, a surface having insoluble basic properties, and to be printed, is treated by the application to it in any convenient manner in a printing pattern of an alkenylsuccinic acid compound; the resulting surface, wet with water, then has a printing ink applied to it and the ink is selectively accepted at only the alkenylsuccinic acid compound treated sites. The ink is permitted to dry in routine fashion and the printing has taken place. In this embodiment, the design is applied by the application of the alkenylsuccinic acid compound to the surface upon which printing is to occur.

It should be noted that, while it is not difficult to render a paper surface basic if desired, many natural paper surfaces will already be sufficiently basic as from the addition of opacifying agents, or hardness minerals left from processing water in manufacture of the paper, and the like. The requirement for a basic paper surface does not require a high basic molarity.

In another embodiment, alkenylsuccinic acid compound is applied selectively in a printing pattern to a surface which has insoluble basic surface properties and which is thereafter water-wetted, and printing ink applied to it; the printing ink is thereafter transferred from the original printing pattern surface site to a second surface such as a piece of paper which is to be printed. In this embodiment, conveniently, the alkenylsuccinic acid compound treated surface can be, in conventional printing fashion, wrapped around a drum in such fashion that, to repeat an imprint, the drum need only to be rotated in contact first with a source of replenishment of surface moisture, thereafter with a source of printing ink, and subsequently in register with a surface such as paper to be printed. It will be recognized that this second embodiment closely approaches the lithographic methods of the prior art but for the present novel chemical means by which the method is made possible and is practiced.

While the foregoing description sets forth the invention understandably, the invention in its entirety is of breadth considerably greater than that set forth immediately hereinabove. 1

In more particular, the alkenylsuccinic acid compound is a compound in which a succinic acid, succinyl chloride, succinic anhydride, or soluble salt of succinic acid bears an alkenyl chain as a substituent, the said alkenyl chain being of from 8 to 16, both inclusive, carbon atoms. The alkenylsuccinyl halides, notably the chlorides, to be used in this invention, are readily prepared from the parent acid by room temperature reaction with thionyl chloride, in the method of Fierz-David et al. See 22 Helvetica Chimica Acta, 82, 86.

In the said alkenyl chain, the position of the ethylenic unsaturation that is characteristic of alkenyl moieties is not critical. The invention is practiced successfully when employing an isomer prepared at substantial expense in which the ethylenic position is precisely known and the purity is high; results when using such pure materials in the present invention, are essentially indistinguishable from results obtained when employing industrial mixed isomers in which location of the unsaturation is incompletely known if it is known at all. Also, mixtures of alkyl and alkenyl substituted, and mixtures of anhydride, acyl halide, acid, and soluble salt or any two of them, so long as adequate amounts of alkenylsuccinic acid compounds are supplied, work practically as well as pure materials.

Among the compounds that are articles of commerce and are usable in the present invention are the following: a mixed hexadecenylsuccinic anhydride represented by the manufacturer as being an isomeric mixture; a relatively pure l-decenylsuccinic anhydride having a refractive index n at 20 C. for the D line of sodium light of 1.469l; a mixed dodecenylsuccinic anhydride as a viscous liquid boiling at l80l82 C. under 5 millimeters mercury pressure absolute; a pure ldodecenylsuccinic anhydride as a crystalline solid melting at 3840 C.; a l-hexadecenylsuccinic anhydride melting at 5960 C.; a tetradecenylsuccinic anhydride melting at 5356.5 C.; and a l,l,3,5-tetramethyl-2- octenylsuccinic anhydride, supplied as a viscous yellow liquid.

Other substances equally adapted to be used include octenylsuccinic anhydride, and didodecenylsuccinic anhydride.

Any of the foregoing can, if desired, be hydrolyzed to obtain the corresponding acid, and, if desired, neutralized with ammonia or an alkalimetal hydroxide, lower alkyl amine or the like to obtain a' corresponding soluble salt and the resulting product used successfully in this invention. The sodium salt is preferred as least expensive, but the lithium and potassium salts can also be used. Representative such succinic acid compounds include l-hexadecenylsuccinic acid, melting at 69-7 1 C. and the other homologues within the indicated scope.

In practice, the alkenylsuccinic acid compound can be applied in any manner that is deemed to be convenient. Thus, when it is desired, as by an artist, to apply the said alkenylsuccinic acid compound to identified sites upon an artists paper, the alkenylsuccinic acid compound may be combined with a stain, dye, marker material, or the like, whereby, through the appearance of color, to designate the site or sites to which the alkenylsuccinic acid compound has been applied. Such colorant, if employed, may be of any desired color but should not, itself, through oiliness, solubility, tendency to crock (yield color under pressure or abrasion) or the like interfere with the printing process. The art of the preparation of pencils, crayons, stick lndia ink and the like is so well known that the choice of a desired site-identifying coloring agent needs no further discussion.

Also, in such application or other applications, when it is desired that the resulting printed material manifest the surface features characteristic of an artist's roughened paper, the alkenylsuccinic acid compound can be applied as by sacrificial abrasion and the like to a paper, canvas, artists board or the like having roughened surface features of any desired form or extent.

Alternatively, the alkenylsuccinic acid compound can be dissolved in any desired solvent, such as water, and applied by a brush. Also, it can, when desired, be applied from an orificeequipped apparatus, such as a pen or pipette in yet another form, the alkenylsuccinic acid compound is transferred in standard printing procedures to the surface of a standard printing plate such as a plate representing metal type converted by routine printing procedures into an electrotype, and thereafter applied in desired pattern to a surface upon which printing is desired. This latter form represents a close parallel to modern offset lithography techniques except for the employment of the chemical agent of the present invention. The manner and practice of transporting and applying the alkenylsuccinic acid compound to a site for printing is not at the heart of this invention but may follow the prior art except for such obvious and insignificant modifications as are evident upon the properties of the alkenylsuccinic acid compound as to solubility, mechanical state and the like.

The printing surface to be employed can be of the greatest variety, whether it is a surface to accept printing finally and directly, or whether it is to serve as a lithograph stone from which other surfaces are then to be printed. Available substances include paper of variety ranging from highly wateracceptive blotting paper to surface-acid-hydrolyzcd parchment papers almost impervious to water; sheets of paperlike plastic, such as plasticized polyvinyl chloride optionally presenting a roughened surface and pigmented as with titanium dioxide or the like; also, metallic surfaces including, notably, surfaces of copper, aluminum, magnesium, lead and its type metal alloys, and the like, as are well known to be used as printing surfaces in the printing, lithography, and etching art.

it is essential and critical to the present invention that such printing surface material have a surface of the property that it is both basic and that the basic moieties be substantially water insoluble under conditions of employment in the present invention; and that such surface be of sufficient mechanical durability to withstand such printing activity as is required of it. For example, a highly water-sensitive tissue paper can be printed according to the present invention, but is impractical to use as a surface to carry printing ink to another surface to be printed. Such considerations, and others equally evident, are routinely and obviously observed within the skill of the art.

As to the basic surface properties of such printable surface material, the term basic" is to be understood with respect to the acidity, or metathetical activity, of the alkenylsuccinic acid, alkenylsuccinic anhydride, or soluble and presumably at least partially neutralized alkenylsuccinic compound, such as succinate salt. Within this definition, then, various substances are available as basic surface materials which substances tend to be amphoteric under conditions other than those of exposure to alkenylsuccinic acid and related compounds. Thus, aluminum hydroxide, and zinc hydroxide are available as basic substances. Also, the basic lead salts, such as basic lead carbonates, especially when securely adherent to a subsurface of lead printing material; the corresponding copper salt of basic character on metallic copper, and similar surfaces on tin, magnesium, and other printing surface materials. These salts of a generally basic character towards acids are all available and are to be used.

In the instance of a plastic paper substitute or paper itself comprising, characteristically, as its predominant structural material, natural cellulose fibers relatively securely felted together, the needed basic surface is readily developed in any of numerous available manners. In one manner useful on paper and similar bibulous substances, the paper or the like is soaked in a water solution of calcium bicarbonate, thereafter dried and gently warmed with release of carbon dioxide to obtain a paper impregnated with calcium carbonate. Also, the paper can be impregnated from aqueous solution with calcium hydroxide. Magnesium salts are available instead of calcium salt when desired. Also, if desired, the paper can be treated as with nitric acid to produce surface carboxyl groups which can be, thereafter, reacted on a basis of approximately one-half equivalent of carboxyl groups per equivalent of polyvalent metallic hydroxide, such as calcium hydroxide, to obtain a fractional salt, such as a half salt, of the polyvalent metal hydroxide bound chemically to the formerly carboxyl-bearing sites of modified paper.

In the case of plastic paper substitute, various treatments are available depending upon the precise nature of the plastic. Basic material can be mechanically incorporated into the plastic substance prior to its extrusion and' calendaring in sheet form. Such basic substance can include calcium hydroxide, calcium carbonate, or other compounds made obvious in view of the availability of these two.

In another form of treatment of the surface of the plastic paper substitute, the surface may be partially dissolved or swollen by the application of a controlled amount of material which, in larger amounts, would be solvent for the said plastic and, while the plastic material is in such solvent-swollen condition, applying to and with pressure pressing into its surface any of a wide variety of insoluble basic substances, including the metallic carbonates and hydroxides hereinbefore noted, numerous amines, including notably primary and secondary amines and the like.

A printing ink to be employed according to the present invention may be of any desired variety provided that, when it is to yield a positive image of the surface treated with succinic acid compound, it is, in general, predominantly characterized by being of a lipophilic character. Printing inks which are bitumen-based, or which make use of hydrocarbon solvents or solvents of which the moietal structure is predominantly hydrocarbonaceous obtain good results. Printing inks in which the vehicle is in the nature of an emulsion representing an aqueous and an oil phase (either of them the continuous and the other the discontinuous), bound by an amphipathic agent, are less desirable. Spirit-based and water-based printing inks are employed in this invention when it is desired to ink the negative, or reverse, of the area treated with alkenylsuccinic acid compound.

The use of water to wet the nontreated surface areas prior to the application of printing ink has been mentioned; water should be of a good grade; free from oily matter, sediment and colored matter, free of substances which tend to bleach or cause chemical reactions in organic materials; and if originally of high mineral content, even though unobjectionable for drinking purposes, mineral content should in some way be reduced; as by passing at least in part through a bed of deionizing ion exchange resins. Wholly de-ionized water is used with good results as is distilled water.

It is impractical to set forth the precise amount of alkenylsuccinic acid compound per unit area of paper or the like to be employed. Substantially larger quantities are employed when it is desired to obtain an entirely black lipophilic, or white hydrophilic, printed area; when, as is often done in works of original lithographic art as well as in the lithographic illustration of magazines, newspapers and the like, it is desired to have areas of the lipophilic lithographcd matter entirely white then no alkenylsuccinic acid compound is to be applied to that area. Gradations between white and black receive varying amounts of the alkenylsuccinic acid compound.

Moreover, the physical properties of paper differ, as to the absolute area as contrasted with the apparent area, a ratio which affords one means of expressing surface roughness. Similarly, the sorptive properties, the bibulous properties and the like of the paper or similar material must be taken into account. In general, smaller amounts of the alkenylsuccinic acid compound are required when the compound is applied as to a reactive metal surface; in general, highly sorptive papers require substantially more. At all events, the amount of alkenylsuccinic acid compound to be applied is an amount such that, upon the subsequent application first of water and thereafter of oil-based printer's ink, it is a sufficient amount to achieve the deposition to the desired weight of ink upon the alkenylsuccinic acid compound treated surface of the printing material. Exact amounts, as measured in milligrams per square centimeter and the like can be ascertained by simple trial and error tests.

When it is desired to achieve only simple designs, such as posters and the like, involving only solid black and clear white letter texts, it is possible to dispose the alkenylsuccinic acid compound in a spray (aerosol") container, and apply it directly therefrom to the printing surface as through a mask or, if desired, without recourse to a mask. From such spray container, the contents can be caused to issue as a solid fine stream, as a continuous foam layer, as a cone spray, or in any other fashion desired.

Also, if desired, the alkenylsuccinic acid compound can be disposed in a thickening vehicle such as a water dispersion of methyl cellulose, or a water dispersion of a neutral salt of carboxymethyl cellulose, or a cross-linked carboxylatebearing polymer such as one of the CarbopoP polymers whereby to present the alkenylsuccinic acid compound in a material of adequate viscosity for each mechanical manipulation, without the addition in fact of substantial additional nonwater solids.

While hydrophilic or lipophilic printing inks are usefully employed, separately or together, it will be, in general, desirable to practice the present invention with little or no recourse to amphipathic agents. Such substances tend, in general, to conduce to degradation of images, blurring of printing, and the like, in the present invention.

The foregoing will enable those skilled in the art to practice the present invention. The best embodiments of this invention now known to the inventor are set forth hereinbelow.

Excess calcium oxide was added to, stirred with, and temporarily suspended in distilled water. The calcium oxide dissolved, in part, as calcium oxide; by reaction with dissolved carbonic acid (from atmospheric CO portions of the calcium compound dissolved as calcium bicarbonate and calcium carbonate; other forms, in trace to very small amounts may have been involved. Excess calcium oxide settled from temporary suspension. 1

A piece of filter paper was routinely disposed in a filtration funnel and the supernatant from the above-described suspension was poured therethrough. In the process, portions of settled calcium oxide were resuspended and carried with supernatant to the filter paper. Drainage was permitted to go forward to substantial completion, and thereafter the resulting paper was air dried. The air-dried paper was lightly tapped and brushed to dislodge and remove solid accumulations of calcium oxide and the like.

The paper was disposed flat upon a relatively impervious surface.

A water solution containing 2.5 percent by weight of solution of n-decenylsucc inic anhydride was prepared and taken up in a pipette. The upper pipette opening was closed, thus lightly retaining the liquid contents therein.

Using the said pipette as though it were a pen, liquid n decenylsuccinic anhydride solution was applied in the pattern of text of letters to the surface of the said filter paper. The resulting paper was permitted to become air dry, was then rewetted by prompt surface application of water (attempting to avoid deep saturation with water) and to the resulting surface were applied various printing inks, all of them based upon hydrocarbonaceous organic solvents together with colorants. The inks were applied with a small piece of spongy elastic material. The ink conspicuously attached to the area treated with alkenylsuccinic anhydride solution, and avoided other areas of the paper. The paper was permitted to become air dry, and, in this condition, had the appearance of having been printed in the pattern applied from the said pipette.

lclaim:

1. Process which comprises the step of applying, in a printing design, an alkenylsuccinic acid compound to a surface on a body having a basic-reacting, water-insoluble material intimately present at the surface thereof, said alkenylsuccinic acid compound being a succinic acid, succinic anhydride, soluble salt of succinic acid, or succinyl halide, said succinic acid compound bearing an alkenyl chain as a substituent, said alkenyl chain being of from 8 to 16, both inclusive, carbon atoms.

2. Process which comprises the steps of applying, in a printing design, an alkenylsuccinic acid compound to a surface of defined area on a body having a basic-reacting, water-insoluble material intimately present at the surface thereof, said alkenylsuccinic acid compound being a succinic acid, succinic anhydride, soluble salt of succinic acid or succinyl halide, said succinic acid compound bearing an alkenyl chain as a substituent, said alkenyl chain being of from 8 to l6, both inclusive, carbon atoms;

wetting the said surface with water, and thereafter applying a lipophilic printing ink thereto; whereby the said printing ink adheres selectively to the printing design areas previously treated with the alkenylsuccinic acid compound.

3. Process of claim 2 wherein, in addition, said surface is then brought into register with and under pressure contacted with a printable surface, whereby said printable surface becomes printed.

4. Process which comprises the steps of applying in a printing design an alkenylsuccinic acid compound to a surface printing ink adheres selectively to the area of the wet surface other than at the areas treated with the alkenylsuccinic acid compound. 5. Process of claim 4 wherein, in addition, said surface is then brought into register with and under pressure contacted with a printable surface, whereby said printable surface becomes printed. 

1. Process which comprises the step of applying, in a printing design, an alkenylsuccinic acid compound to a surface on a body having a basic-reacting, water-insoluble material intimately present at the surface thereof, said alkenylsuccinic acid compound being a succinic acid, succinic anhydride, soluble salt of succinic acid, or succinyl halide, said succinic acid compound bearing an alkenyl chain as a substituent, said alkenyl chain being of from 8 to 16, both inclusive, carbon atoms.
 2. Process which comprises the steps of applying, in a printing design, an alkenylsuccinic acid compound to a surface of defined area on a body having a basic-reacting, water-insoluble material intimately present at the surface thereof, said alkenylsuccinic acid compound being a succinic acid, succinic anhydride, soluble salt of succinic acid or succinyl halide, said succinic acid compound bearing an alkenyl chain as a substituent, said alkenyl chain being of from 8 to 16, both inclusive, carbon atoms; wetting the said surface with water, and thereafter applying a lipophilic printing ink thereto; whereby the said printing ink adheres selectively to the printing design areas previously treated with the alkenylsuccinic acid compound.
 3. Process of claim 2 wherein, in addition, said surface is then brought into register with and under pressure contacted with a printable surface, whereby said printable surface becomes printed.
 4. Process which comprises the steps of applying in a printing design an alkenylsuccinic acid compound to a surface of defined area on a body having a basic-reacting, water-insoluble material intimately present at the surface thereof, said alkenylsuccinic acid compound being a succinic acid, succinic anhydride, soluble salt of succinic acid or succinyl halide, said succinic acid compound bearing an alkenyl chain as a substituent, said alkenyl chain being from 8 to 16, both inclusive, carbon atoms; wetting the said surface with water, and thereafter applying a hydrophilic printing ink thereto; whereby the said printing ink adheres selectively to the area of the wet surface other than at the areas treated with the alkenylsuccinic acid compound.
 5. Process of claim 4 wherein, in addition, said surface is then brought into register with and under pressure contacted with a printable surface, whereby said printable surface becomes printed. 